Update doc analytics

docs/mkdocs.yml

@@ -26,11 +26,7 @@ theme:
     prev: 'Previous'
     next: 'Next'
 
-copyright: "Copyright © 2016-2019 Containous"
-
-google_analytics:
-  - 'UA-51880359-3'
-  - 'docs.traefik.io'
+copyright: "Copyright © 2016-2020 Containous"
 
 extra_css:
   - assets/styles/extra.css # Our custom styles

docs/theme/main.html

@@ -1,5 +1,15 @@
 {% extends "base.html" %}
 
+{% block analytics %}
+<!-- Google Tag Manager -->
+<script>(function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':
+            new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],
+        j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src=
+        'https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);
+    })(window,document,'script','dataLayer','GTM-NMWC63S');</script>
+<!-- End Google Tag Manager -->
+{% endblock %}
+
 {% block footer %}
 
 {% import "partials/language.html" as lang with context %}
@@ -34,4 +44,4 @@
     </div>
 </footer>
 
-{% endblock %}
+{% endblock %}